I've tried using it over the years but I never liked it because there was no information. So last night I looked at my local city and there is almost no information at all. I spent a few hours last night adding buildings and restaurants and removing incorrect items. It was actually kind of fun and therapeutic and I plan to do more of it tonight. My girlfriend thinks it's dumb and I'm wasting my time because Google maps and Apple maps and Bing maps exists but she just doesn't understand open source.
Edit: Apologies, I just realized this question is not Linux specific.
I started because I needed a customizable online map for a website and no map out there was really complete where I needed. So instead of waiting for commercial services, I started to log ways using GPS and add them to OSM.
The simplest way is to trace it on the starllite imagery available on the editor built-in to osm.org. If it's not visible there, here is the wiki's list of Android apps that can record GPS tracks, and it's not hard to find the other pages on the wiki about getting those off your phone and into the map. Some of those apps can probably do that bit for you, I've just never tried
You have to use data you created yourself. It is not allowed to use proprietary data from Google. If you use Android, then the Vespucci app may help you. Allows to log the way and then directly add it.